A typical write head structure for a magnetic disk system is schematically illustrated in FIG. 1. Its principal parts are lower pole 12 and upper pole 11 (commonly referred to as P1 and P2, respectively. These are magnetically connected at one end and separated by a small non-magnetic layer 13 (the write gap) at the other end. The track width will be defined by the P2 width at the gap. P1 may be notched through a self aligned process, known as partial pole trim (PPT), to better define the written transitions. Coil 14 is located in the space enclosed by P1 and P2 and is the source of the magnetic field that is focused by the two pole pieces. All seen in the figure is a magnetic shield layer 16 which is electrically isolated from the lower pole by dielectric layer 15.
FIG. 2 shows a variation on the basic design seen in FIG. 1. In this case a secondary upper pole 21 is ‘stitched’ in between 11 (P2) and gap 13. This is for ease of fabrication so that the track width definition can be done on relatively flatter topography. An additional feature, not present in the design of FIG. 1, is shallow trench 22 which is etched into lower pole 12. Since trench 22 has sloping sides, the depth to which it is etched can be used to fine tune the length of lower pole 12 that is part of the write gap 13. This is usually referred to as the throat. This allows for a further concentration of the available flux within the write gap. In the stitched pole design, the track width is defining part of pole 21 as well as the back gap connection 23 which are fabricated immediately following the deposition of write gap 13.
FIG. 3 is an isometric view of part of FIG. 1 or FIG. 2 as seen when looking up from the magnetic track at the air bearing surface that passes over it (so-called ABS view). It is important to note that the surfaces of the upper pole (11 in FIG. 1 or 21 in FIG. 2), the gap 13, and the lower pole 12, are all coplanar. One consequence of this, the standard structure in use today, is the unintended erasure of adjacent tracks on the disk as narrower tracks and higher track densities are developed. Most improvements that have been proposed, such as increased PPT depth, smooth P1 topography, and narrower gap all come with either process challenges or reduced on track writeablity performance.
As track densities increase, the read head extracts the recorded information from an ever decreasing narrow track. It becomes increasingly important not to affect the integrity of this narrow track of data. In the structure shown in FIG. 3, P2 has magnetic material confined to the written track. P1. however, still includes material that extends outside the track width (TW) defining region. This may lead to unintended writing on an adjacent track and may therefore affect the data integrity of the system.
A routine search of the prior art was performed with the following references of interest being found:
U.S. Pat. No. 6,353,511 B1 (Shi et al.) shows a process for a improved Write head. U.S. Pat. No. 5,878,481 (Feng et al.) shows a pole trimming process for a write head. U.S. Pat. No. 5,843,521 (Ju et al.) and U.S. Pat. No. 5,802,700 (Chen et al.) are related patents. U.S. Pat. No. 5,652,687 (Chen et al.) shows a planarized write head process.